According to Jim Marshall, they were all smiling because he told them ” I’m the only person in this state with any coke and if you want some you better smile”. That’s what is being covered up in Duane Allman’s hand ( I think that’s who it is ).
The shoot was actually done in Georgia before the tour started.
John Varvatos now owns most of Jim Marshall’s collection and the original sheet can be seen at the store in Las Vegas.